Synthesis of Charge-Compensated Octacarbonyltriruthenium Monocarbollide Complexes

The charge-compensated monocarbon carboranes nido-7-NR3-7-CB10H12 react with [Ru3(CO)12] in toluene at reflux temperatures to give the triruthenium complexes [Ru3(CO)8(η5-7-NR3-7-CB10H10)] [NR3 = NMe3 (1a), NH2But (1b), and NMe2But (1c)]. The molecular structure of 1a has been established by X-ray crystallography. The metal atoms form an essentially isosceles triangle. One Ru atom carries two terminal CO groups and the nido-7-NMe3-7-CB10H10 cage, coordinated in a pentahapto manner. The two boron atoms in the β-sites with respect to the carbon in the CBBBB ring form exopolyhedral three-center, two-electron B−H⇀Ru bonds to the other two Ru atoms. These metal atoms also carry three essentially terminally attached CO ligands. Treatment of 1a with PPh3 in toluene gave, after column chromatography of the mixture, [Ru3(μ-H)(μ3-σ: η5-7-NMe3-7-CB10H9)(CO)7(PPh3)] (2), whereas reaction with CNBut affords [Ru3(CO)7(CNBut)(η5-7-NMe3-7-CB10H10)] (3). The structure of 2 has been established by X-ray crystallography. Th...